A typical rock drill comprises a shank adapter, percussion device and rotating device. A drill string can be fastened to the shank adapter, to which rotation torque is transmitted from the rotating device by means of the shank adapter and impact pulses are transmitted from the percussion device. The percussion device generally comprises a reciprocating percussion piston arranged to provide impacts to an impact surface located outermost at the back end of the shank adapter.
This type of drill has a certain minimum length and, in practice, it cannot be made shorter than the minimum length. The minimum length is determined by the length of the percussion piston and shank adapter, the stroke length of the percussion piston and the remaining structure of the drill, such as the end covers. When quarrying in low spaces, for instance in tunnels, it is advantageous to use as short a drill as possible so as to be able to use drill strings of a practical length, especially for upwards drilling. However, the length of the drill cannot be shortened without shortening the length of the percussion piston and shank adapter. If the percussion piston is made very short, it is no longer possible to provide therewith the impact pulses needed to break rock, and the performance of the drill is substantially reduced. The shank adapter, too, should have a certain length so that drill strings can be firmly fastened to it and that it can be firmly supported in the body of the drill. In addition, the rotation torque required to rotate the shank adapter should be transmitted to the shank adapter. The stroke of the percussion piston also cannot be shortened very much without a harmful effect on the impact pulses transmitted to the shank adapter.
It is expensive to produce conventional one-piece shank adapters having splines at the back end, and a coupling, e.g., a thread or a hexagonal connector, at the free end for connection with the drill string. Moreover, since the adapter is a part that needs relatively frequent replacement, due mainly to wearing at the coupling (free) end thereof, there may be appreciable costs associated with the use of such drills.
An object of the invention is to provide a rock drill having a shank adapter that can be replaced more easily and at less cost.
It is another object of the present invention to provide a novel and improved rock drill shank adapter for percussive rock drilling.
Another object of the present invention to provide a novel and improved rock drill shank adapter for percussive rock drilling that is easily replaceable.
Still another object of the present invention to provide a novel and improved rock drill shank adapter for percussive rock drilling that is replaceable without dismounting the drill.
Another object of the present invention to provide drill string components for percussive rock drilling that are easily replaceable.